how much does barrel heating affect accuracy?

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futureranger

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I have a savage 10fp with a medalist varmint stock and I was shooting it this weekend and was surprised how much my group shifted after about 20 shots (shooting about 1 shot every 2 minutes) right out of the case with my zero from the weekend before it was shooting ½” low, grouping about .75” at a 100 yards. But as I started shooting more to the right until it was off by nearly 2”. The barrel was warm to the touch but not hot. The scope is a millett trs-1 not great but has held a 0 pretty well in the past so I don’t think it is scope. Could a heating barrel really move bullet that much? Thanks for the help
 
That was Elmer Keith's complaint about the Garand back before WW II -- apparently it was a LOT more than 2" when they first tried out the new design.

Heat can certainly change POI. However, it might be something you can fix on a particular gun.
 
It depends on barrel thickness, caliber, and the particular gun. Sporter barrels can go from 1 moa to 3 moa, after 20 rounds. While bull barrels take about 50.
 
How is the barreled action bedded in the stock?

AFAIK that matters a lot. If the barrel is seated in the stock with uneven pressure, or an otherwise free-floated barrel is touching the stock somewhere, this can magnify the effect.
 
its aluminum block bedded, came with the B&C medalist stock, i also had the tang free floated
 
Skim coat it with a regular bedding compound. The aluminum block is a good starting point but it can't be perfect for every rifle. You won't have to add much material and you shouldn't have to take any off before you bed but it still should get bedded.

Also do you have any other scopes you could substitute in place of the Millet? Not sure its a scope I would trust on something .30 caliber.
 
As ArmedBear mentioned, is the stock touching the barrel anywhere?
Are your action screws properly tightened?
IMO, a bull barrel shot at that pace should not wander shots due to heat.
Something else might be contributing to the POI change.

NCsmitty
 
i'll recheck everything again, but when i put on the stock and scope i had them both set at 65inch/pounds. on one side the barrel is really close to the stock but i can still get paper through it. also i was sitting out in the open on a sunny day, and the whole rifle was warm from the sun but i didnt think of it before. should i have more stock removed to get a better free-float?(my uncle is a gunsmith)
 
I have a M1896 Swede that walks in elevation as the barrel heats. That sucker changes about 12" in elevation at 100 yards.

Bedded the thing, played round with handguard fit. It is the barrel. There is some stress in the barrel that makes the thing walk.

Which explains how this 1924 vintage rifle was in mint condition. No one wanted to shoot it.
 
also, a lot of dudes forget to recheck the freefloat, AFTER IT HEATS UP!!!!
if you have just one teeneh , wee lattle spot touching now, then it is going to fly way off!
 
Try the above (checking the freefloat hot and cleaning)...then make sure everything is tight. I don't think the stock is the problem so long as it is sufficiently torqued, B&C make pretty good stocks (and from all accounts the 10fp is pretty decent as well). If it fails to improve replace the scope and mounts if you have others available (at least scope). Keep the scope at one power and do not adjust it if no others are available.
 
If the problem is consistent then there's no way the scope is causing it. It may simply be that you have internal stress in the barrel. In that situation, heat changes the stiffness of the steel which allows a straight barrel to go crooked all by itself, even if it's freefloated. The real solutions are to either cryo treat your barrel or replace it with a higher quality piece. A bandaid is to put a pressure patch up near the front which will put some stress on the barrel, but it will be consistent stress and may eliminate the walking.
 
I have a Savage 12FV.
Within about 25 shots it moved 1/2 inch right and a bit up (I forgot how much but on the order of 1/2 inch or less) at 100 yards.

Also, something bad was happening with the front swivel. Maybe hitting the rest on recoil. When I removed it, the deepest threads were gone, and my groups suddenly got better.


3 shot groups are currently running a hair under 0.5 inch at 100 yards. Some bugeyes (3/16" C-C) and some above 0.5 " c-C.

I think you have something going wrong with yours; something is touching when it heats up.
 
Internal stress in the barrel is a possibility. Bedding is a possibility. Most likely not the scope. Keeping the temp of the ammo the same is helpful too.
Try changing the torque on the front receiver screw. Then try dampening the barrel at different spots and with different pressures with different lengths and methods. Or you could just get a Kreiger barrel and shoot little bitty holes.
 
I wonder if steam is issuing from that shop. That would be one way to do it.

Anyhoo all barrels have some change when under thermal conditions. That is one reason Main battle tanks use a laser on the end of the barrel to compute the shift after the shot and add that value to re-lay the rifled bore onto the target.
 
it has only happened on my last few trips to the range when it was >80 degrees out and i was in the sun for a little while. im going to take off some more stock this weekend around the barrel and re check the torques. thanks for all the help guys
 
After you fire a shot, are you closing the bolt and chambering a round immediately or pausing between shots with the bolt open? If you're closing the bolt and chambering a round, the heat of the barrel can heat up the round in the chamber. This can increase the velocity which will affect the point of impact. Also, as the barrel heats up you'll notice more mirage through your scope which can affect your point of aim. Just some things to consider in addition to those already mentioned.

:)
 
I've seen barrels get so hot that they will cook off a round if you leave it in a few seconds.
Click to expand...
If that happens after 20rnds in a bolt gun...there is a major issue :neener:
 
Before going after the stock with a grinder, put some felt tip pen on your barrel and check your clearances. If they look good cold, then go shoot and do it again. Be minimal in what you take off. You want as much meat in your forearm as you can have without having any contact.
 
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